The third in a series of films featuring François Truffaut's alter-ego, Antoine Doinel, the story resumes with Antoine being discharged from military service. His sweetheart Christine's father lands Antoine a job as a security guard, which he promptly loses. Stumbling into a position assisting a private detective, Antoine falls for his employers' seductive wife, Fabienne, and finds that he must choose between the older woman and Christine.

A judge investigating police corruption finds that the deeper he digs, the more roadblocks he finds.

A rich kid, the daughter of an oil tycoon, lives a life of luxury. Bad guys kidnap the heiress.

Philippe Lambert, an attractive young attaché to the Prime Minister's office, is a man of many female conquests. One of them, Madame Grandbourg, wife of a very influential man, sent him a passionate letter, which he lost at the theater. Marion, the usherette who found it, contacts him to ask him for a "favor" in exchange for its return: to avoid eviction from the family apartment, because of the father, who gardens in every room and constantly floods the downstairs neighbors. At first, Lambert refuses to give in to the "blackmail" and calls in the police to unmask the indelicate woman, but love soon gets in the way...

Julien Bouin, a former typographist, and his wife Clemence, who used to perform in a circus, hardly talk to each other in their small house, soon to be demolished. His cat Greffier being the only one he still gives affection to, he becomes the object of Clemence's anger.

Prosecutor Etzel discovers that his father has sentenced a man, Leonardo Maurizius, on mere presumptions. He then makes it a point of honor to trace the sources of the case to uncover the truth.

Three weeks before his wedding to Virginie, Vincent receives a letter from Magasins Réunis telling him to pick up a gift. He goes there and receives a baby, Olivier, 18 months old...

Jean, a married 40-year-old filmmaker, and his young working class lover, Catherine, engage in a circular series of spectacular blow-ups and tentative reunions, their mutual desire a fire that burns them again and again.

André Loriot works for Dr Clairac in a laboratory producing euphoric pills. He searches in vain for an apartment where he can settle down and start a family with the woman who loves him, Juliette. To motivate himself and cope with the setbacks he encounters, he decides to swallow an excessive dose of euphoriants.

Hubert de Tartas' life becomes a complete muddle when his wife's grandfather is unearthed after having spent 65 years in frozen hibernation in the polar circle. After being de-frosted, the Hibernating Man believes it is still the beginning of the century. Nothing is spared to keep that illusion alive. At the end of his rope, Hubert blurts out the truth and takes the man from Edwardian times on a crazy spree through an ultramodern Twentieth Century.